Electron discharge tube with partially coated grid



March 16,1948.

ELECTRON DISCHARGE TUBE WITH PARTIALLY COATED GRID Filed April 22, 1946 EDZMRD GERAPDUSJJORGEZO INVENTOR Y I I.

ATTORNEY E. G. DQRGELO 1 Patented ar. 1%, i948 ELECTRON DISCHARGE TUBE WITH PARTIALLY COATED GRID Eduard Gerardus Dorgelo, Eindhoven, Netherlands, assignor, by me sne assignments, to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application April 22, 1946,

In the Netherlands April 11,

Serial No. 663,821 I 1942 Section 1, Public Law 690, August 8, 1946 Patent expires April 11, 1962 3 Claims. (Cl. 2502'7.5)

For the purpose of utilising the gas-combining action of zirconium it is known to provide this metal on portions of grids of electric discharge tubes or to make these grids entirely or in part of this material. In these cases the provision of zirconium results in a large decrease of the secondary emission compared with the usual grid materials, since the secondary emission of this metal is considerably less than that of the grid materials generally in use, such as nickel or molybdenum.

In the copending application :Serial No. 662,964 filed April 18, 1946, it has been set out by the applicant that in particular cases, viz particularly with modern transmission valves in which larger current densities and lower voltages are operated with than in the earlier tubes it is desirable and even necessary to admit an appreciable secondary emission, since otherwise an excessive positive grid current would be set up in the use of the tube, or in other words with these modern tubes it is not desirable that the grid surface should be coated completely with zirconium.

In the said prior specification it is then suggested to apply zirconium to the parts of the grid remote from the cathode, the side adjacent the cathode being entirely or substantially uncoated.

Further researches have now revealed that even other grid parts may be coated with zirconium without the disadvantages hereinbefore outlined occurring thus, a discharge tube according to the invention comprises a grid which is partially coated with zirconium and which carries zirconium on the surface, adjacent the cathode, of the active parts of the grid opposite the centre of the cathode and/or on the supporting members of the grid.

It has been found indeed that since in this case the idea in question is not to decrease the secondary emission excessively it is sufficient when the ends of the grid, that is to say those points where the space charge has a minimum and the secondary emission a maximum value, are not coated with zirconium or else the supporting rods are coated with zirconium, that is to say those component members of the grid which with a given construction of this electrode hardly attract any electrons and thus whether or not coated practically do not bring about any alteration in the secondary emission.

The coating possibilities here outlined may also be combined with a coating on that side of the grid which is remote from the cathode, as is described in the above-mentioned prior specification. Thus, the constructional advantage is obtained that it is possible for given grid elements, such as the central turns to be provided on all sides with a zirconium layer, as may be efiected for example in the form of a zirconium sheath, although use may be made of zirconium in a finely powdered state.

The invention may be used with advantage in tubes for generating electric oscillations, for example in transmission valves having an artificially cooled anode. Since the coating of such an anode entails great difliculty and the low temperature also prevents a good gas-combining action one has to rely with these tubes on a grid as the carrier of the zirconium.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawing, in which one form of construction of a part of a discharge tube according to the present invention is schematically represented.

Referring to the single figure of the drawing, l designates the cathode, 2 the control grid and 3 the anode; as indicated at l only the central turns, that is to say those turns which are opposite the centre of the cathode, are coated on all sides with zirconium. As indicated hereinbefore, many further combinations are possible.

I claim:

1. An electron discharge device comprising in successive arrangement a cathode, a grid and an anode, and gettering material covering solely the cathode side of that portion of said grid in the vicinity of the central area of said cathode.

2. An electron discharge device comprising in successive arrangement a cathode, a grid and an anode, and a zirconium getter covering solely the cathode side of that portion of said grid in the vicinity of the central area of said cathode.

3. An electron discharge device comprising in successive arrangement a cathode, a grid and an artificially cooled anode, and a zirconium getter covering solely the cathode side of said grid in the vicinity of the central area of said cathode.

EDUARD GERARDUS DORGELO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,368,060 Wooten Jan. 23, 1945 FOREIGN PATENTS Number Country Date 749,053 France May 2, 1933 

